Treatment of slaughtered animals by injecting a treatment solution into the circulation system of the slaughtered animals provides for improved meat quality and improved yield. Such processing, also called “rinsing,” involves the removal of the blood from the animal and the introduction of the treatment solution into the circulatory system. An example apparatus for administering a treatment solution to animals such as cattle, horses, hogs, poultry, deer, buffalo, sheep among others is described in U.S. Pat. No. 5,007,336, and is incorporated herein by reference. An example slaughtering process is described in U.S. Pat. No. 5,964,656, and is incorporated herein by reference.